Secondary oxalosis due to excess vitamin C intake: a cause of graft loss in a renal transplant recipient.

Renal oxalate deposition can be seen with primary hyperoxaluria, malabsorptive states, ethylene glycol toxicity and, rarely, with excessive vitamin C ingestion. We report a case of secondary hyperoxaluria in which the diagnosis was not considered initially because there was no past history of urinary calculi and no evidence of nephrocalcinosis on plain X-ray of the abdomen and ultrasonography. The disease was detected and diagnosed only after kidney transplantation. Secondary oxalosis can cause graft loss or delayed graft function. Biopsy of the allograft should be carefully examined for oxalate deposits even in the absence of a family history. When oxalosis is diagnosed, intensifying hemodialysis (HD) to eliminate calcium oxalate can help in the recovery of renal function in some cases. Systematic vitamin C supplementation in HD patients should be avoided as it can be a cause of secondary oxalosis.

Kinetic analyses guide the therapeutic decision in a novel form of moderate aromatic Acid decarboxylase deficiency.

BACKGROUND: Aromatic amino acid decarboxylase (AADC) deficiency is a rare autosomal recessive disorder resulting in a combined dopamine and serotonin deficiency. About 50% of the cases set in the neonatal period. Here, we report an atypical clinical presentation with moderate symptoms. PATIENT: At 10months old, the patient presented paroxysmal eye movements without seizures, and feeding difficulties which were attributed to gastroesophageal reflux. She was investigated at the age of 7years, because of orofacial dyspraxia, hypomimie, axial hypotonia and focal segmental dystonia, bilateral ptosis, without evidence for cognitive impairment. RESULTS: HVA [110nM; (reference value (rv): 202-596)] and HIAA (12nM; rv: 87-366) decreased, OMD (520nM; rv: 5-60) and 5-HTP (56nM; rv: 2-16) increased in CSF. We confirmed the diagnosis of AADC deficiency because the activity in plasma was low: 4pmol/min/ml; rv: 16-137. The kinetic analysis revealed a sixfold increase in the apparent affinity for L-dopa (4.26mM; control=0.71), but the V (max) was unchanged (37.5pmol dopamine/min/ml; control=39.1), suggesting a modification in the substrate binding-site. Molecular analysis revealed two heterozygous mutations in the DDC gene: c1040G > A; pR347Q already described, and a novel mutation c478C > T, pR160W. CONCLUSION: (1) CSF neurotransmitters metabolites suggested a moderate AADC deficiency; (2) The initial velocity saturation curve for L-dopa displayed a cooperative ligand binding behavior, in keeping with the modifications of the three-dimensional structure, induced by the amino acid substitutions (3) The treatment combination of L-dopa with pyridoxine dramatically improved the quality of life, the fatigability, and the paroxysmal eye movements.